IMPROVEMENT EXPERIMENT OF NONSANDSTONE RESERVOIRS OF QIANJIANG FORMATION IN THE QIANJIANG SAG, THE JIANGHAN BASIN

Nonsandstone reservoirs between salt beds of Qianjiang Formation in the Qianjiang Sag of the Jianghan Basin are mainly composed of dolomicrite,glauberite rock,mudstone and their peperite.Porosity and permeability are commonly poor.In the experiment,sample No.4 of Member 2 of Qianjiang Formation in Well Wangyun 10-6(glauberite-bearing dolomicrite) and sample No.8 of Member 3 of Qianjiang Formation in Well Wangping 1(dolomite-bearing fine-medium crystalline glauberite) are processed with 3 different solutions:saturated saline water,mixture of saturated saline water and acetic acid,and mixture of saturated saline water,acetic acid and hydrochloric acid.Capillary pressure curves indicate that,expulsion pressures of the processed samples No.4 and No.8 decrease by 62% and 88% respectively.Maximum pore-throat radiuses increase by 187% and 743% respectively.There is obvious improvement in sorting coefficient of pore-throat too.In addition,porosities of both samples increase by over 100%.The experiment shows that,skeleton of the processed samples maintains intact,while porosity and permeability are improved effectively.